Hashimotos: The Most Common Cause of Hypothyroidism

Hashimoto’s, also known as Hashimoto’s Thyroiditis, is considered to be the most common cause of hypothyroidism. It is an autoimmune disorder that causes your thyroid to produce less than optimal amounts of hormones. The body needs these hormones to regulate its metabolism and other functions. Follow us along as we discuss what Hashimoto’s is and how it relates back to Hypothyroidism.

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The thyroid is a small gland in the front of your neck. It releases hormones that affect everything in the body, from heart rate to energy levels. Hormones produced in the thyroid include T3 and T4, two of the most important thyroid hormones. These hormones are responsible for growth, development, metabolism (the rate at which all chemical processes in the body take place) and many other functions throughout your body.

T3 specifically helps with the thermal regulation of the body and is essential for growth, development, and general homeostasis (stable state).

The thyroid gland produces T4 and then converts it into T3; this conversion process can be inhibited by inflammation. When your body is inflamed (for example, due to injury or illness), your thyroid may not produce enough T3. 

When your thyroid is not working optimally, this can result in an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism).

Thyroid hormones are responsible for many functions throughout the body, including regulating metabolism. It is not rare to see low levels of thyroid and rapid weight gain in the same individual.  Let’s discuss common types of thyroid disorders. 


Hyperthyroidism is when you have an overactive thyroid gland that generates too much thyroid hormone. This results in symptoms such as:

· Fast heart rate

· Increased appetite

· Excessive perspiration

· Weight loss

· Nervousness, irritability, and/or anxiety

· Diarrhea

· Sensitivity to heat

· And more!


Hypothyroidism is when you have an underactive thyroid gland that does not generate enough thyroid hormone. This results in symptoms such as:

· Fatigue and excessive sleepiness

· Weight gain or inability to lose weight

· Depression, mood swings, and/or irritability

· Muscle pain and stiffness

· Cold intolerance

· Constipation and dry skin

· And more!

Primary, Secondary, Tertiary, and Subclinical Hypothyroidism

There are different types of hypothyroidism. 

  • Primary Hypothyroidism: is when the thyroid gland itself does not maintain adequate levels of T3 or T4. This can be caused by a number of things, but the most common cause in the US is Hashimoto’s Disease. In primary hypothyroidism the problem is with the thyroid itself.
  • Secondary Hypothyroidism: is when the pituitary fails to produce enough Thyroid-Stimulating Hormone (TSH) in response to low levels of thyroid hormone in the blood. This can be caused by pituitary disease, hypothalamic disease, medications that reduce TSH (such as amiodarone or lithium), autoimmune destruction of the pituitary, and more. In secondary hypothyroidism, the issue is not with the thyroid but the  pituitary, which monitors the thyroid.
  • Tertiary Hypothyroidism: is when the hypothalamus fails to produce enough thyrothropin-releasing hormone (TRH).  TRH is needed to stimulate the pituitary to produce enough TSH. TSH is necessary to stimulate the thyroid gland. Research shows that this can be caused by hypothalamic disease, medications that reduce TRH (such as lithium), autoimmune destruction of the hypothalamus, and more.
  • Subclinical hypothyroidism: is an early, mild form of hypothyroidism. Usually, your thyroid is functioning properly but your TSH levels are slightly elevated. This form of hypothyroidism is most common in women, the elderly, and those with other autoimmune diseases.


The most common cause of hypothyroidism is Hashimoto’s.  It’s important to note that Hashimoto’s and hypothyroidism are not the same conditions. People who have Hashimoto’s often progress to hypothyroidism, or an underactive thyroid.  But not always. Sometimes people can be diagnosed with both at the same time, while some might only ever experience Hashimoto’s and never develop hypothyroidism. Hashimoto’s is an autoimmune disorder. Autoimmune disorders are when your body’s immune system starts attacking healthy cells. In the case of Hashimoto’s, this is when you have an immune system that incorrectly identifies the thyroid gland as something foreign and attacks it, resulting in damage to your thyroid. 

Although Hashimoto’s most often results in hypothyroidism, it can also cause hyperthyroidism, when your thyroid gland is overactive. However, this form of hyperthyroidism may go undetected because some of the symptoms are similar to that of people with Hashimoto’s who present with hypothyroidism (such as weight gain, fatigue, lethargy, lack of concentration).  

What are the symptoms of Hashimoto’s? 

Hashimoto’s is usually asymptomatic for years which makes it difficult to diagnose. One of the first signs of this disease would manifest through fatigue, which is the most common symptom. Other symptoms include weight gain, feeling cold all the time, constipation, and depression.  

With Hashimoto’s, symptoms will worsen as your disease progresses and it becomes harder to recover from them. 

People with Hashimoto’s typically present with:

· A goiter (an enlarged thyroid)

· Decreased TSH levels

Hashimoto’s is caused by antibodies attacking the thyroid, which causes it to not produce enough hormones. The specific triggers for this attack are unknown but there are some ideas on why this happens. Some research links Hashimoto’s to genetics, exposure to viruses and environmental toxins, chronic inflammation, gut health issues, diets high in goitrogens, obesity, soy, and bacterial or viral infections. There is also a belief that Hashimoto’s may be brought on by stress hormones.

Hashimoto’s is important to address because left untreated, it can lead to an underactive thyroid or hypothyroidism. The thyroid gland is responsible for producing thyroxine which is responsible for regulating your metabolism. It also affects the way you use energy, the way your body uses food for energy, how your body molds fat and sugar, as well as how your heartbeats. An underactive thyroid can have long-term health effects such as weight gain, anxiety, lethargy, and depression. 

Personalized Approach to Hashimoto’s

Generally, your health care provider will take your medical history and perform a physical exam. Additionally, they will check your Thyroid Stimulating Hormone (TSH) and your Free T4 (FT4) levels. 

At the Institute for Human Optimization, we believe the best way to help our patients is by having all the insight we can get access to. This in turn helps us create a personalized, precise, protocol unique to you. 

Some blood tests we will look at include but are not limited to:

  • Checking levels of Thyroid peroxidase Ab, Thyroglobulin Ab, and TPO-ab. These are antibodies that are fighting against your thyroid gland.  
  • Total T4 will be reviewed to look into the levels of protein that the thyroid gland produces. 
  • Total T3:   the active form of thyroid hormone 
  • Free T3: the active form of thyroid hormone 
  • Reverse T3: Reverse T3 is a protein that binds to T3. When this happens it makes T3 not available for the body to use, which will make your thyroid gland slow down production of thyroid hormone.
  • Thyroid Binding Globulin: Thyroid Binding Globulin will be tested to look for levels of protein that your thyroid gland produces.  
  • Thyroglobulin Antibodies: the presence of this antibody is a marker for Hashimoto’s disease.

People with Hashimoto’s, or autoimmune hypothyroidism, have special needs when it comes to thyroid hormone replacement therapy.  It can be difficult to find the right type of medication for you – what might work well in one person may not work at all in another patient. 

Disclaimer: The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Additionally, the information provided in this blog, including but not limited to, text, graphics, images, and other material contained on this website, or in any linked materials, including but not limited to, text, graphics, images are not intended and should not be construed as medical advice and are for informational purposes only and should not be construed as medical advice. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Before taking any medications, over-the-counter drugs, supplements or herbs, consult a physician for a thorough evaluation. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this or any website.

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